Water dispersible granular herbicidal compositions comprising dinitroaniline and imidazolinone herbicides with montmorillonite carriers

ABSTRACT

The present invention relates to water dispersible granular compositions comprising a dinitroaniline herbicide and an imidazolinone herbicide with a montmorillonite carrier, and to a process for the preparation of the compositions. Such compositions are storage stable and possess desirable dispersion properties.

This is a continuation-in-part of applications Ser. No. 07/996,412,filed on Dec. 23, 1992, now U.S. Pat. No. 5,296,450, and Ser. No.07/996,221, field on Dec. 23, 1992 now U.S. Pat. No. 5,294,594.

BACKGROUND OF THE INVENTION

Water dispersible granules (WDG's) are becoming increasingly importantin the formulation of agricultural compositions because they are moresafely handled and environmentally friendly than other commonly usedformulations. For example, chemical spills of WDG's are easily cleaned,no toxic solvents are present in the WDG formulation, and it is possibleto package WDG's in water soluble packaging, thus reducing userexposure.

The typical processes for making WDG's are pan granulation, spraydrying, fluid bed granulation, and mixing agglomeration. The choice ofwhich process to use depends on several factors, including the physicaland chemical properties of the active ingredient(s), environmental andsafety aspects, and volume and packaging requirements.

Pan granulation typically produces compositions having gooddispersibility and can be used for low-melt, active ingredients. Thedisadvantage of pan granulation is that the granules are often dusty,and the size distribution of the granule is difficult to control. Spraydrying typically produces compositions in high volume and with gooddispersibility, however, the bulk density of the product is usually lowand it is difficult to spray dry low-melt, active ingredients. Fluid bedgranulation has basically the same advantages/disadvantages as spraydrying, while mixing agglomeration has similar advantages/disadvantagesas pan granulation.

Dinitroaniline herbicides, which are useful for the selective control ofcertain grasses and broadleaf weeds, have typically been formulated asemulsifiable concentrates, flowables, wettable powders or the like,which are diluted in a tank mix. These formulations, however, requirehandling, measuring and mixing prior to application to the soil.

Conventional dispersible granular compositions containing dinitroanilineherbicides have been difficult to prepare. Such herbicides, which aresolid at room temperature but have melting points below 100° C., have atendency to cake, fuse or lump up when stored at or exposed to elevatedtemperatures, due to the excessive softening or partial melting of theherbicides. Moreover, they are often dusty and may cause staining.

The imidazolinone class of herbicides, such as imazaquin, imazethapyr,imazamethapyr and imazamethabenz-methyl, are highly desirable for theselective control of a wide variety of grass and broadleaf weeds in thepresence of agricultural crops at exceptionally low rates ofapplication. At present, imidazolinone herbicides are commerciallyavailable mainly in the form of liquid compositions. However, asenvironmental concerns increase, there is an ever-growing need for aneffective granular composition containing an imidazolinone herbicide.The prior art's pan granulated compositions present the common drawbacksof dusting, variable particle size distribution, and lack of ease ofwater dispersibility.

Efforts to produce stable granular formulations comprising suchdinitroaniline herbicides, alone, or in combination with imidazolinoneherbicides, without the drawbacks discussed above, and capable ofuniform distribution in a solvent-free, WDG formulation, however,continue.

It is therefore an object of this invention to provide a solvent-free,water dispersible granular composition with improved dispersionproperties.

It is also an object of this invention to provide a water dispersiblegranular composition comprising a novel dispersion enhancing agent.

It is another object of this invention to produce a non-dusting,non-staining, water dispersible granular herbicidal composition havinggranules of substantially uniform size and density.

It is yet another object of this invention to provide storage stablewater dispersible granular herbicidal compositions comprising one ormore active ingredients.

It is further object of this invention to provide a novel method forproducing water dispersible granular herbicidal compositions.

These and other objects of this invention will become more evident inthe detailed description that follows.

SUMMARY OF THE INVENTION

The present invention relates to water dispersible granular compositionscomprising a dinitroaniline herbicide, alone, or in combination with animidazolinone herbicide, and a dispersion enhancing agent, and to aprocess for the preparation of said compositions. Such compositions arestorage stable and contain desirable dispersion properties.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a novel formulation of useful dinitroanilineherbicides, alone, or in combination with imidazolinone herbicides, aswater dispersible granular compositions (WDG's), which offer ease ofhandling coupled with reduced dusting, and other environmentallydesirable characteristics.

A primary concern when formulating WDG's is that the granules dispersein an acceptable amount of time. Of the conventional carriers typicallyconsidered, bentonite was among the least desirable with which toformulate a WDG because the granules are difficult to disperse. However,it has now been found that extruding the WDG with a dispersion enhancingagent permits the use of bentonite because of its compatibility withlow-melt, active ingredients, such as dinitroaniline compounds.Advantageously, the use of bentonite minimizes the loss of the physicalperformance attributes of low-melt, active ingredients, such asdinitroanilines, compared to most other typical carriers. At the sametime, such a stable formulation permits the coformulation of adinitroaniline herbicide and an imidazolinone herbicide, therebybenefiting from the desirable and complementary properties of eachactive ingredient.

As used herein, the term "dispersion enhancing agent" means a chemicalentity that facilitates the swelling and dispersing of the bentonite orother suitable carrier component of the WDG composition of theinvention. Typically, such dispersion enhancing agents are selected frombases, such as alkali metal hydroxides and amines, and water swellablepolymers, including cellulosic materials.

It has now been found that extrudable granulated herbicidal compositionscomprising a dinitroaniline herbicide, alone, or in combination with andan imidazolinone herbicide, and a dispersion enhancing agent, can beformulated to possess improved suspendability and dispersibility. Such adiscovery takes advantage of the beneficial properties of manycomponents while minimizing potential incompatibility.

In a preferred embodiment, the present invention relates towater-dispersible granular compositions comprising a dinitroanilineherbicide of structural formula (I) ##STR1## wherein R₁ is selected fromH, C₁₋ C₄ straight or branched-chain alkyl, C₃₋ C₄ alkenyl and C₃₋ C₄alkynyl; R₂ is selected from C₁₋ C₆ straight or branched-chain alkyl andoptionally substituted with Cl or OCH₃, C₃₋ C₄ alkenyl, and C₃₋ C₄alkynyl; R₃ is H, CH₃ or CH₂ OCH₃ ; and R₄ is C₁₋ C₄ alkyl, CF₃ or Cl,alone, or in combination with an imidazolinone herbicide. Theimidazolinone herbicide may be any of the imidazolinone compounds knownin the art such as those described in U.S. Pat. Nos. 4,798,619;4,772,311; 5,039,333; 5,108,485; and in EP 254,951 and EP 322,616.Preferably, the imidazolinone herbicide is selected from imazaquin,imazapyr, imazethapyr and imazamethapyr. A more preferred imidazolinoneherbicide is imazaquin. The present invention also relates to methods ofproducing WDG compositions containing such compounds.

More preferred formula (I) herbicides for use in the compositions of theinvention include pendimethalin(N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine) and trifluralin(N,N-dipropyl-2,6-dinitro-4-trifluoromethylaniline), as well asbenfluralin, isopropalin, ethalfluralin, oryzalin (Ryzelan®) and thelike, alone, or in combination. Pendimethalin and trifluralin are mostpreferred.

In general, WDG's containing high concentrations of between about 20%and 90%, preferably between about 30% and 70% by weight, of low-meltingdinitroanilines, such as pendimethalin and trifluralin, optionally incombination with about 1% to 20%, preferably 5% to 15% by weight of animidazolinone herbicide, and a carrier, such as bentonite, may beprepared in a controlled manner by extrusion in the presence of adispersion enhancing agent, such as a base or water swellable polymer,to yield essentially dust-free and uniformly granular WDG's possessinggood dispersibility. Compositions containing such high concentrations ofactive ingredients, particularly when used in combination, provide theenvironmental and commercial advantage of using less material to obtainthe desired result. Lower concentration pesticidal compositions,however, may also be prepared, as can compositions containing mixturesof active ingredients, depending on the needs of the particularapplication.

The finding that bentonite clay is suitable for preparing heat-stable,water dispersible granular compositions containing high concentrationsof low melting materials is unexpected. It is contemplated that theincorporation of between about 0.5% and 20% by weight, preferablybetween about 1% and 10% by weight, of a base, such as sodium hydroxide,potassium hydroxide or isopropyl amine, or water-swellable polymers, forexample, heterocyclic polymers such as Agrimer® XLF (2-pyrolidinone,1-ethenyl, homopolymer, or PVP), N-vinyl-2-pyrrolidonel(NVP), acellulosic material, such as croscarmellose sodium (e.g., Ac-Di-Sol®,FMC Corporation), microcrystalline cellulose (e.g., Lattice® NTC-80), orother commercially available polyhydroxy polymers, into the WDGformulation causes the bentonite or other suitable hydrous carrier toswell upon contact with the water. Advantageously, this swelling permitsthe WDG to disperse more quickly.

Carriers suitable for use in the preparation of the water dispersiblegranular compositions of the invention include swelling clays such askaolinate, zeolite and preferably, montmorillonite clays, such asbeidellite, bentonite, nontronite and saponite. Most preferred arecarriers comprising bentonite, at least in greater part, as carriercombinations may be employed. Commercially available, naturallyoccurring swelling clays include VOLCLAY® (Wyoming Bentonites), VEEGUM®,or other naturally occurring swelling clays which contain the samemontmorillonite unit structure and properties.

Suitable wetting agents for use in the preparation of the WDGcompositions of the invention include conventional agents such as sodiumN-methyl-N-oleyoyltaurate (Igepon® T-77), octylphenoxy polyethoxyethanol, nonylphenoxy polyethoxy ethanol, sodium dioctyl sulfosuccinate,sodium dodecyl benzyl sulfonate, sodium lauryl sulfonate, and the like,or mixtures thereof. Suitable suspension agents include conventionalagents such as sodium lignosulfonate, alkyl naphthalene sulfonates, thesodium salt of a naphthalene sulfuric acid-formaldehyde condensate(Morwet® D-425 or Lowmar® PW), and the like, or mixtures thereof(Morwet® EFW). Suitable antifoaming agents include conventionaldetergents such as sodium tallowate (Foamaster Soap L®) and the like.Suitable flow agents include conventional agents such as fumed silica,calcium silicate (Micro-Cel® E), and the like, or mixtures thereof.

The WDG compositions of the invention comprise about 20 to 90% by weight(preferably 30-70%) of a dinitroaniline compound, preferably adinitroaniline compound of formula (I), optionally about 1% to 20%,preferably 5% to 15% by weight, of an imidazolinone herbicide,preferably selected from the group consisting of imazaquin, imazethapyr,imazamethapyr and imazapyr, admixed with from about 5.0 to 25.0% byweight of one or more carriers, about 1.0-7.5% by weight of one or morewetting agents, about 2-10% by weight of one or more suspension agents,and about 0.5-20% by weight of one or more dispersion enhancing agents.More preferably, the WDG compositions of the invention also include upto about 1% by weight of one or more antifoaming agents, and up to about7.5% by weight of one or more flow agents to facilitate the extrusionprocess.

The hardness, sorptivity, particle size and apparent density of the WDGcomposition can be adjusted by varying or combining the type(s) of clay,the type(s) of surfactants and/or wetting agents, and mixtures thereof,which are commonly employed in agricultural formulations. Otherconventional formulating agents, such as disintegrating aids orthickening agents, may also be added to the WDG compositions of theinvention while maintaining the desirable properties described above.

In order to prepare the WDG compositions of the invention, theappropriate dinitroaniline, and optionally imidazolinone, technicalmaterial is passed through a pin mill. The milled technical is thenblended with the wetting agents, the suspension agents, and thecarriers, and optionally, the anitfoaming agents and the flow agents.The blended material is milled in an air classifier mill, preferablyunder liquid nitrogen or other unreactive refrigerant source sufficientto cool the mill. The milled material is then mixed with water (10-15%of total batch size) and the dispersion enhancing agents, and extrudedthrough a conventional LUWA bench top basket extruder, for example, onehaving about a 0.6 mm to 1.2 mm aperture. The extruded granules areallowed to dry overnight in a hood until the residual moisture isreduced to about 1-3%. The granules are then sieved through a #16 and#40 mesh screen and collected.

Many variations of this invention will occur to those skilled in the artin light of the above, detailed description. For example, combinationsof water swellable polymers may be used as the dispersion enhancingagent. All such obvious variations are within the full intended scope ofthe appended claims.

The present invention is further illustrated by the followingnon-limiting examples.

EXAMPLES Experimental Procedures

The preparation of WDG compositions of the invention for comparisontesting with prior art compositions involved (a) milling about 20% to90% by weight of a dinitroaniline herbicide, optionally with about 1% to20% by weight of an imidazolinone herbicide; (b) blending the milledherbicide with about 1% to 7.5% by weight of one or more wetting agents,about 2% to 10% by weight of one or more suspension agents and about 5.0to 25.0% by weight of one or more carriers; (c) milling the blendproduced by step (b), preferrably in the presence of an unreactiverefrigerant sufficient to cool the mill; (d) mixing about 0.5% to 20% byweight of one or more dispersion enhancing agents with water, and themilled blend produced by step (c); (e) extruding the milled blend intogranular compositions; and (f) drying the extruded granularcompositions.

Following the above procedures, the following WDG compositions wereprepared and tested. The important physical properties of the WDGcompositions of Examples 1-7 (dinitroanaline herbicides alone) andExamples 8-14 (dinitroanaline herbicides in combination withimidazolinone herbicides) are set forth in Examples 15-16.

    __________________________________________________________________________                  (% wt./wt.)                                                     Ingredient    1   2   3   4   5   6   7                                       __________________________________________________________________________    Pendimethalin 66.7                                                                              62.7                                                                              60.0                                                                              56.7                                                                              66.0                                                                              66.0                                                                              66.3                                    Tech. (91%)                                                                   Calcium Silicate                                                                            5.0 4.7 4.5 4.2 5.0 5.0 5.0                                     Sodium-N-Methyl-N-                                                                          2.5 2.4 2.2 2.1 2.5 2.5 2.5                                     Oleoyltaurate                                                                 Sodium Naphthalene                                                                          5.0 9.7 9.5 9.2 5.0 5.0 5.0                                     Formaldehyde Sulfonate,                                                       concensate                                                                    Bentonite Clay                                                                              16.0                                                                              15.0                                                                              14.4                                                                              13.8                                                                              15.7                                                                              15.7                                                                              --                                      Kaolin Clay   4.3 4.0 4.0 3.6 4.3 4.3 20.7                                    Sodium Tallowate                                                                            0.5 0.5 0.4 0.4 0.5 0.5 0.5                                     2-Pyrrolidinone, 1-Ethenyl,                                                                 --  1.0 5.0 10.0                                                                              --  --  --                                      Homopolymer                                                                   Sodium Hydroxide                                                                            --  --  --  --  1.0 --  --                                      Sodium Chloride                                                                             --  --  --  --  --  1.0 --                                                    100%                                                                              100%                                                                              100%                                                                              100%                                                                              100%                                                                              100%                                                                              100%                                    __________________________________________________________________________

    __________________________________________________________________________                     (% wt./wt.)                                                  Ingredient       8   9   10  11  12  13  14                                   __________________________________________________________________________    Pendimethalin    54.1                                                                              59.2                                                                              62.7                                                                              54.1                                                                              55.5                                                                              63.4                                                                              58.2                                 Tech. (91%)                                                                   Imazaquin        8.9 9.0 --  8.9 9.1 --  9.2                                  Tech. (97.5)                                                                  Imazethapyr      --  --  4.5 --  --  4.0 --                                   (97.5%)                                                                       Calcium Silicate 4.0 4.4 4.7 4.0 4.1 4.1 4.0                                  Sodium-N-Methyl- --  2.2 2.3 --  --  --  --                                   N-Oleoyltaurate                                                               Sodium Dioctyl   --  --  --  2.2 --  --  --                                   Sulfosuccinate                                                                Sodium Naphthalene                                                                             5.9 4.4 4.7 5.9 --  3.0 5.1                                  Formaldehyde Sulfonate,                                                       condensate                                                                    Sodium Naphthalene                                                                             --  --  --  --  --  1.0 3.2                                  Sulfonate/Alkyl                                                               Carboxylate blend                                                             Bentonite Clay   21.4                                                                              14.5                                                                              15.0                                                                              21.4                                                                              12.9                                                                              15.4                                                                              13.1                                 Kaolin Clay      3.5 3.7 4.0 3.5 3.6 4.1 3.7                                  Sodium Hydroxide --  2.6 2.1 --  --  --  --                                   Potassim Phosphate                                                                             --  --  --  --  9.1 --  0.8                                  (Tribasic)                                                                    Croscarmellose Sodium (internally                                                              --  --  --  --  3.8 4.0 2.3                                  crosslinked Sodium Carboxymethyl                                              Cellulose)                                                                    Microcrystalline --  --  --  --  1.9 1.0 0.8                                  Cellulose                                                                                      100%                                                                              100%                                                                              100%                                                                              100%                                                                              100%                                                                              100%                                                                              100%                                 __________________________________________________________________________

EXAMPLE 14 Evaluation of Dispersibility and Temperature Stability of theTest Compositions

Test compositions are stored at room temperature, 45° C. or 50° C. for 7days, or up to 3 months, prior to evaluation. A predetermined amount oftest composition, typically 1 gram or quantity sufficient to representthe maximum end use concentration, is added 100 mL of water in agraduated cylinder, which is then quickly stoppered. The cylinder isimmediately rotated (inverted) 180° , and, after a 3 second pause,rotated an additional 180° , and held for 3 seconds. The cycle is thenrepeated. The number of 360° cycles required to completelydissolve/disperse the granules is recorded. The procedure is continueduntil 30 inversions have been made. The desired quick dispersion of thegranules is reflected by the lower number of inversions (Table 1).

                  TABLE 1                                                         ______________________________________                                        Dispersibility (# of Inversions)                                              ______________________________________                                        Example                                                                              7 days @ RT 7 days at 45° C.                                                                     7 days @ 50° C.                       1      18          17            20                                           2      18          17            18                                           3      14          12            10                                           4      13           8             5                                           5      12          11            11                                           6       5          14            12                                           7      22          23            28                                                  Initial @ RT                                                                              3 months @ 45° C.                                   8       5          >30                                                        9       6          14                                                         10      6           6                                                         11      5          24                                                         12      8          12                                                         ______________________________________                                    

EXAMPLE 15 Evaluation of Suspendibility of Test Composition

Test compositions are stored at room temperature, 45° C. or 50° C., for7 days prior to evaluation. A predetermined amount of test compositionis dispersed in a controlled aqueous system and allowed to settle for 30minutes. An aliquot is taken from center of the suspension and thesolids content is measured. The 30 minute reading is compared to, andreported as a percentage of, the presettling value. The desiredsuspendibility property of the composition is reflected by a higherpercentage.

                  TABLE 2                                                         ______________________________________                                        Suspendiblity (% Suspended)                                                   Example                                                                              7 days @ RT  7 days at 45° C.                                                                   7 days @ 50° C.                        ______________________________________                                        1      85.6         84.9        68.2                                          2      82.3         83.8        70.3                                          3      79.2         83.0        68.6                                          4      79.7         78.2        64.7                                          5      82.2         83.5        68.8                                          6      29.6         --          --                                            7      86.9         22.2        17.8                                          ______________________________________                                    

As the results demonstrate, the WDG compositions of the inventionpossess improved dispersibility and suspendibility compared to the priorart formulations.

We claim:
 1. A water dispersible granular composition comprising on aweight to weight basis about 20% to 90% of a dinitroaniline herbicide,in combination with about 1% to 20% of an imidazolinone herbicide; about5% to 25% of a montmorillonite carrier; about 1.0% to 7.5% of a wettingagent; about 2% to 10% of a suspension agent; and about 0.5 to 20% of adispersion enhancing agent.
 2. The water dispersible granularcomposition according to claim 1 wherein the dispersion enhancing agentis selected from a base and a water swellable polymer.
 3. The waterdispersible granular composition according to claim 2 wherein the baseis selected from an amine and an alkali metal hydroxide.
 4. The waterdispersible granular composition according to claim 3 wherein the baseis selected from the group consisting of sodium hydroxide, potassiumhydroxide and isopropyl amine.
 5. The water dispersible granularcomposition according to claim 2 wherein the water swellable polymercomprises 2-pyrrolidinone, 1-ethenyl, homopolymer.
 6. The waterdispersible granular composition according to claim 2 wherein the waterswellable polymer comprises cellulosic material.
 7. The waterdispersible granular composition according to claim 6 wherein thecellulosic material is selected from the group consisting ofcroscarmellose sodium and microcrystalline cellulose.
 8. The waterdispersible granular composition to claim 1, further comprising up toabout 1% by weight of an antifoaming agent and up to about 7.5% byweight of a flow agent.
 9. The water dispersible granular compositionaccording to claim 1 wherein the dinitroaniline herbicide is selectedfrom the group consisting of pendimethalin, trifluralin, isopropalin,ethalfluralin, benfluralin and oryzalin.
 10. The water dispersiblegranular composition according to claim 1 wherein the imidazolinoneherbicide is selected from imazaquin, imazethapyr, imazamethapyr andimazapyr.
 11. The water dispersible granular composition according toclaim 1 wherein the carrier is selected from the group consisting ofbeidellite, bentonite, nortronite, saponite, and mixtures thereof. 12.The water dispersible granular composition according to claim 11 whereinthe carrier comprises bentonite.
 13. A method for the production of adinitroaniline-containing water dispersible granular composition havingimproved dispensability comprising the steps of:(a) milling about 20% to90% by weight of a dinitroaniline herbicides with about 1% to 20% byweight of an imidazolinone herbicide; (b) blending the milled herbicidecombination produced by step (a) with about 1% to 7.5% by weight of oneor more wetting agents, about 2% to 10% by weight of one or moresuspension agents and about 5% to 25% by weight of one or moremontmorillonite carriers; (c) milling the blend produced by step (b) inthe presence of an unreactive refrigerant sufficient to cool the mill;(d) mixing about 0.5% to 20% by weight of one or more dispersionenhancing agents with water and the milled blend produced by step (c);(e) extruding the milled blend into granular compositions; and (f)drying the extruded granular compositions.
 14. The method according toclaim 13 wherein the dinitroaniline herbicide is selected from the groupconsisting of pendimethalin, trifluralin, isopropalin, ethalfluraline,benfluralin and oryzalin.
 15. The method according to claim 13 whereinthe imidazolinone herbicide is selected from the group consisting ofimazaquin, imazethapyr, imazamethapyr and imazapyr.
 16. The methodaccording to claim 13 wherein step (b) further comprises the addition ofup to about 1% by weight of one or more antifoaming agents and up toabout 7.5% by weight of one or more flow agents.
 17. The methodaccording to claim 13 wherein the dispersion enhancing agent is selectedfrom the group consisting of a base and a water swellable polymer. 18.The method according to claim 17 wherein the base is selected from thegroup consisting of amines and alkali metal hydroxides.
 19. The methodaccording to claim 17 wherein the water swellable polymer comprises2-pyrrolidinone, 1-ethenyl-, homopolymer.
 20. The method according toclaim 17 wherein the water swellable polymer comprises a cellulosicmaterial.